Popular Science Monthly/Volume 59/August 1901/The Pose of the Body as Related to the Type of the Cranium and the Direction of the Visual Plane
|THE POSE OF THE BODY AS RELATED TO THE TYPE OF THE CRANIUM AND THE DIRECTION OF THE VISUAL PLANE.|
By GEORGE T. STEVENS, M.D.. Ph.D.
IT is a novel proposition that the position of the head in respect to the body or of the shoulders in reference to the back, that the carriage of the whole body in walking and the attitude of a person in conversation, should be governed in an important measure by the form of the cranium. It will also, doubtless, be regarded as a bold assertion to say that all these positions and attitudes and even the gait of individuals are largely modified, even in many instances controlled, by the normal position of the eyes in respect to the cranium. Yet it is not difficult to show that both these propositions are true and that the truth contained in these statements is not only of importance as a principle in art, but that it is of great practical value from the point of view of the well-being of large classes of persons.
From the standpoint of art the principle involved in these propositions shows the error of representing individuals who have certain forms of crania in attitudes which, for persons with those special cranial characteristics, would be unnatural and almost absurd. For example, when Thorwaldsen represented Sir Walter Scott with his chin elevated high in the air, he gave to the distinguished author of Waverley a posture of the head which would have been not only painful, but almost impossible for him to have maintained as a characteristic pose.
From the more practical and more important standpoint it may even be said that, owing to the position of the visual plane in respect to the head, there may be comparative immunity from certain complaints and diseases or a comparative predisposition to those very affections according to the type of the head and the direction of the normal plane of vision.
In order to facilitate the examination of the topic, it will be necessary to define some of the terms and some of the principles-which enter into it.
The term 'normal plane of vision' will be used, and it should at the outset be understood exactly what is meant by the phrase.
By the term 'normal plane of vision' as here employed, it is intended to express the direction which the lines of sight would assume, the head being in the erect, or more technically in what is known as the primary, position, in case no muscular effort should be made to change the eyes from an entirely passive adjustment.
Under these conditions the line of sight of each of the two eyes lies in an imaginary plane which may be coincident with, or somewhat higher than, or somewhat lower than, the plane of the horizon.
The normal plane of vision differs essentially from the primary plane of regard of Helmholtz and other writers, for this plane of regard refers to the plane formed by the two visual lines when these lines are directed toward the horizon, the head being in the primary position. The plane of regard is therefore unalterable. It was my own privilege to show that the normal plane of vision not only varies in different individuals but that, as a general rule, this variation is associated with and controlled by certain cranial characteristics which will presently engage our attention.
This leads us to the consideration of certain types of the human cranium as they are recognized by craniologists.
While the form of the head of an individual may not be so clearly of one or another type that it must be classified as belonging to a certain group, in general, heads are grouped into three great classes or types, and these classes or types are again divided into subtypes. In this connection the subtypes need not be taken into consideration, but some knowledge of the main types is essential.
Craniologists, then, classify crania as long, broad and medium. Medium skulls, in order to avoid misconception, will be here designated as tall skulls, since the term medium does' not, in this relation, refer to capacity, but to certain special measurements, and the accepted term might be misleading to those not well versed in the subject.
The basis for the classification consists of the proportion which the longest diameter from before backwards bears to the longest transverse diameter. If the transverse diameter is 75⁄100 that of the longer diameter or less than 75⁄100 the head is said to be in the class of long heads; but if the transverse diameter equals or exceeds 85⁄100 the length of the skull, it is a broad skull. Medium skulls, or, as we are now to call them, tall skulls, are those in which the transverse diameter is between 75⁄100 and 85⁄100 and, as might be supposed, the measurement from the base of the skull to its summit, while it may not of itself be greater in an individual case than that of one of the long or one of the broad type nor even so great, is greater in proportion to the other measurements.
The diagrams, Figs. 1, 2 and 3, give the general outline of the form of heads of these types when looked at from above.
|Fig. 1. The Long Head.||Fig. 2. The Tall Head.||Fig. 3. The Broad Head.|
In typical heads belonging to either of these types the outline of the face is likely to be characteristic of the type. Thus, the general outline of the face from the line of the brows to the tip of the chin as seen from the side differs, as a rule, according to the type of the cranium. Associated with the long cranium there is generally a convex facial outline, while a side view of the face of one from the class of tall heads shows usually very little or no curve. On the other hand the face of one from the class of broad skulls is likely to show a concave line.
The next series of figures, 4, 5 and 6, gives an idea of the general form from a side view of each of these three types in the living subject.
|Fig. 4. The Long Head.
Facial angle 10°.
|Fig. 5. The Tall (medium) Head. Facial angle 0°.||Fig. 6. The Broad Head.|
To nearly all general laws affecting the form of the human body there are exceptions, and the rule just stated is not absolutely uniform in its application. However, the type of head and the outline of face are generally in the relation shown by the diagrams.
In these three classes of crania the normal visual plane does not as a rule occupy the same position in relation to the horizontal plane, but varies according to the type of skull.
The relation of the normal visual plane to the type of the cranium in each of the three classes may be arrived at by direct and by indirect methods.
In the case of the living subject, the dimensions of the head may be taken and the plane of vision established in the same individual. The determination of the plane of vision in the living subject is accomplished through the aid of an instrument known as the tropometer. The relation is thus established by a direct method. The indirect method is that of ascertaining the direction of the imaginary line constitutingthe axis of the orbit in the prepared skull, the measurements of which are known. The orbits are more or less cone shaped. If the extreme apex of the cone, at which the optic nerve enters it, is taken as one point of the line of the axis, and a point where two straight lines drawn at nearly right angles with each other from certain parts of the circle of bone constituting the outer border of the orbit cross is taken as another point in the line of the axis, the line which would pass through these two points would represent the axis. This imaginary line, if projected forward and beyond the orbit, would be seen in most cases to point somewhat downward, the skull being in the primary position, and in some types of skulls it points much more downward than in other types.
It is interesting to find that the pointing of the imaginary line representing the axis of the orbit closely corresponds with the observations on the normal visual plane in the living subject.
The interest is more considerable when it is found that the form of the orbit in the different classes of skulls offers an explanation of the peculiarities in the direction of the orbital axis, as well as of the normal plane of vision.
Figs. 8, 9 and 10 represent the front views of skulls of the long, tall and broad types respectively, showing the form of the orbit corresponding to each type. It will be seen that in the long skull (Fig. 8) the roof of the orbit is much lower than that of the tall skull (Fig. 9) and that the lower border extends more downward. The orbit of the tall skull is not only placed with its opening higher, but it is more narrow from side to side. In the case of the broad skull (Fig. 10) the roof of the orbit is low like that of the long skull, but the lower border does not extend so far downward and the direction of the transverse diameter is more oblique.
Measurements of the direction of the axis of the orbit in these three classes show that in the long skull the direction is usually quite
Front view of Long Skull:
Front view of Tall Skull:
Front view of Broad Skull:
low, that in the tall skull it is much higher and that, while the axis of the broad skull is lower than that of the tall one, it is scarcely as low on the average as in the case of the long skull; and these comparative positions of the axes of the orbits in the prepared skulls correspond remarkably with the positions of the visual plane in the case of living subjects with heads of corresponding types. That is, the visual plane of the long head is low, of the broad head also low and that of the tall head is high.
Notwithstanding the apparent simplicity of these relations of the form of the orbit with the type of the skull and of the direction of the visual plane to the type of cranium, there are, in practice, certain modifying features.
The most important of these from the anatomical standpoint is found in the angle of the face. In forming a judgment, therefore, of the probable direction of the normal visual plane in the living subject without resorting to measurements by the tropometer, it is necessary to measure or to estimate this angle. None of the measurements employed for the prepared skull will serve the purpose here, and it has been found most practical to use for fixed points for the measurement of this angle the following: the glabella, which is the elevation above the root of the nose and just between the ridges of bone above the orbits; the depression just below the nose, and the tip of the chin.
If these three fixed points are selected for the measurement of the angle of the face, it will readily be seen that this angle varies greatly in different individuals. It may, indeed, vary considerably in heads belonging to the same type. Yet, on the whole, there is a pretty general association between the character of the face and the type of the head.
In the case of the long head, for example, the angle is external, as will be seen on turning to the diagram, Fig. 4, in which the facial angle is plus (+) 11°, or to Fig. 14where it is plus () 15°. In the broad head, on the contrary, the angle is likely to be inverse, as in Fig. 6 where the angle is minus ()) 10°. In the tall head, however, the facial angle almost vanishes. It is, in general, 0° as in Fig. 5 or only an angle of from 2° to 4°, rarely exceeding 6°. But, as already intimated, the angle may vary in each type of head.
Now, if the angle of the face is taken in connection with the type of head, we have a fairly certain indication of the direction of the plane of vision.
With the long head and strong external facial angle the plane of vision is almost invariably low. With the broad head and inverse angle the visual plane is also low, but there is a restricted downward range of the rotations of the eyes, notwithstanding this depressed position of the visual plane. With the tall head and straight face the plane of vision is high and in proportion as the head is comparatively tall it may be very high.
When these elemental principles are once understood it is not difficult to comprehend the phenomena to which they give rise.
Thus it is easy to see that a person whose normal plane of vision is quite low finds it easier to throw the head backwards, lifting the chin and forcing the forehead back, than to raise the visual plane to the level of the horizon or even to the lower plane which the eyes assume in walking, if that visual plane has to be thus elevated and the elevation maintained for some time by the delicate muscles which act directly in elevating the eyes. On the contrary one whose visual plane is very high prefers to throw the forehead in advance and the chin into the breast rather than maintain a tension upon the little muscles which act directly upon the eyes to pull them down.
Thus it will be seen that the person represented at Fig. 12, with the long head (from before backward) and the strong angle of the face, carries the forehead quite far back and the chin well up, not from any affectation of attitude, but because it is less wearisome to the eyes to assume this position. As a matter of fact this person's eyes were normally adjusted 10° below the plane which has been found to be the
best and which may be called the standard plane. On the contrary the person whose pose is represented at Fig. 13, whose head is high compared to its transverse and horizontal diameters, a head which is neither of the long nor broad type, but of the medium (tall) type with the absence of a strong angle of the face, had the plane of vision very high. Such a person prefers to throw the forehead in advance and the chin into the breast, rather than make a continual and somewhat tiresome effort to draw the eyes to the proper plane by direct tension upon the depressor muscles of the eyes.
It is not difficult to see that this selection of the easiest method of adjusting the lines of sight to surrounding objects exercises a commanding influence on the whole pose of the body.
While the rule generally holds that the form of the skull and therefore the form of the orbit governs the direction of the visual plane and hence also the pose of the head and of the body, there are other elements which enter into the case and give rise to exceptions. The most important of these modifying elements is the condition known as the 'declination of the vertical meridians of the retina'; still, in order to avoid taking too wide a range of discussion, we shall treat the subject as though the influence of the plane of vision were in all cases uniform, which is not strictly the case; yet, for our present purpose, we may omit the exceptions, and the statements that follow must be accepted as general and as including the proviso, other things being equal.
Examining then the pose of the head and body in their relations to the position of the visual plane more in detail, it will be found that when the visual plane is quite low not only is there a tendency for the individual to elevate the chin and throw the head back, but the muscles of the whole back, even those of its lower 'part, are put in a state of tension. This tension is so considerable that in a great many instances among persons who are not very strong the resulting habitual pains of the muscles engaged are often mistaken and treated for diseases of internal organs or of the spine year after year.
An element of the facial expression with this direction of the visual plane is the pronounced elevation of the brows upon the forehead and the somewhat drooping appearance of the eyelids (see Fig. 4). There are other facial expressions characteristic of this depressed plane of vision which may be passed over in this connection.
The attitude and gait of the individual are also generally influenced by the downward direction of the visual plane. In walking the shoulders are thrown back and the chest is thrust forward. The foot, in many cases, swings forward considerably beyond the limit of the completed step, so that it is drawn somewhat backward as it comes to the ground.
While persons of this class are more liable than others to certain physical complaints and nervous disturbances which can be traced directly to this ocular condition than are those whose eyes are adjusted for a higher plane, they are, on the other hand, compared with this latter class far less subject to certain other forms of diseases and affections.
A single example will serve to illustrate this proposition. Although the illustration relates to a trouble with the eyes themselves it would be easy to present many examples to illustrate immunity of the same class of persons from a variety of more general affections.
A few years since a distinguished oculist of one of our southern cities announced that trachoma, that form of eye trouble commonly known as granular lids, and which is one of the prolific sources of blindness, is unknown among pure negroes. The discussion of this proposition, after occupying the attention of oculists for some time, was at length taken up in a different way by a distinguished colleague in Constantinople.
This gentleman wrote to oculists in all parts of the world asking for the results of their observations in their own countries in regard to all classes of people. He at length published a symposium of the answers showing the prevalence of trachoma in different countries and among the different classes of people. As given in this contribution there seemed to be a confused accumulation of facts which had, on the whole, apparently little meaning. Peoples of contiguous countries, of the same color and not very different in habits of life, were reported as differing widely in respect to the prevalence of the affection. No reasons were assigned and none seemed to be suggested by the varying facts. An analysis which I made of this report showed that among peoples with the 'medium' or tall heads, like the Irish and the Italians, trachoma is rife; while among peoples with the broad head, like the Bavarians, or with the long head, like the negroes whose ancestors were from the West or Guinea coast of Africa, trachoma did not prevail; but it is interesting to note that descendants of the negroes of the northern part of Africa, where the heads of the natives are often tall, are subject to trachoma equally with the whites among whom they live. I have in another connection discussed this question at more length.
A glance at Fig 14 will show that the negro as he is known in our Southern States not only throws the head backward in the manner characteristic of the long head, the strong facial angle and the depressed visual plane, but that the eyebrows are characteristically elevated. This drawing up of the brow is accompanied with a drawing upon the lids and hence no pressure is brought upon the surface of the eyes by the upper lids. In the case of the tall head with the high plane of vision the brows are strongly compressed and the lids bind upon the eyeball and thus in the midst of dust and filth or even in good sanitary surroundings disease of the lids may be promoted. Reverting once more to the declinations of the retinal meridians, the same effect may be induced both as to the pose of the head and the relaxed state of the lids. It is, however, impracticable to consider the subject from that point of view at present.
Turning to a larger and more important subject, the negro is known to be especially subject to tubercular diseases, yet he is, to an unusual degree, immune from consumption. In my investigations during the past few years, I have not seen a consumptive the direction of whose visual plane was not much higher than the standard. We shall come to this from another point of view. It is easy to see that the principle which applies in the case of the long skull applies similarly also in that of the broad skull although, in general, in somewhat less degree.
People who have broad heads with inverse angle of the face usually carry the head with the forehead thrown back and the chin elevated. Those who have this form of head and this consequent depression of the visual plane often suffer from the neuralgic or myalgic affections of the back of the head and the spinal region like the class with the long head and strong exterior facial angle. The differences need not be discussed here.
Directing our attention now to the excessive upward direction of the plane of vision which is found principally with the tall, or more correctly and technically, the mesocephalic head, we find not only a great difference in the adjustments of the facial muscles as compared with the class which we have just considered, but also in the poise of the body. In the class now to be considered the brows are compressed and the expression is one of intensity. The chin is not elevated as in the other class, but the forehead is advanced and the body leans forward. The shoulders bend forward and the chest is often compressed. With the noblest form of the head comes a stoop of the body. Fortunately for the world these people do not all have consumption, for if they did one of the highest forms of development of humanity would be wiped out. Unfortunately, however, it is from this class of people that consumption finds the great majority of its victims. Glance at the position of the air passages in these two portraits in each of which the habitual pose of the body and head is fairly represented.
In the case of the one with the broad head and difficult upward rotations of the eyes (Fig. 15), a swarm of tubercle bacilli would pass in and out of the respiratory passages with much the same effect as any other minute particles of dust, while in the case of the tall headed boy (Fig. 16) who has, by actual measurement, the visual plane adjusted more than twenty degrees above the horizon, the larynx forms a hinge-like valve and in the quiet eddies of a lung under these circumstances the tubercle bacilli can easily hold high carnival. If the direction of the large branches of the air tubes is considered it is evident that the circulation of the air in the very upper portions of the lungs of one with such a habitual pose would naturally be even less active than in the lower parts, and it is interesting to remember that it is in the upper lobes that the bacilli usually commence their inroads. The modern treatment of consumption is fresh air. It is evident that the amount of air admitted to the lungs of a person with the habitual attitude of this boy must be very materially modified by this position of the head; and could the normal pose be improved he would by that means be subjected to the fresh-air treatment. It will be seen that this is entirely practicable.
The comparative immunity of the negro race from consumption has already been referred to, and it is a fact of much practical interest that among the people of Iceland, people with the extreme broad head and with the characteristic pose, the head thrown back, the chin elevated, consumption is unknown. Yet these people habitually inhale the most vitiated atmosphere, an atmosphere which, habitually inhaled by the people of this country, would induce an epidemic of consumption which would be of the most devastating character.
As the general pose of the head and the attitude of the body differ in the class with high heads from those of the other classes, so the gait and carriage of these people differ widely from those of the others. If the cake walk is an extravagant exaggeration of the walk of the classes with the low visual plane, the stoop of Shylock as it is represented on the stage is the exaggeration of the carriage of the other class.
This is but a most cursory glance at a most important subject; and the affections and characteristics mentioned are but a group of those whose name is legion and which have for their cause one or other of these visual conditions.
Several years ago attention was called by the writer of this article to the one-sided carriage of the head of those who have the visual line of one eye higher than that of the other. I will only refer to it here as one of the elements in this interesting subject.
The practical question which arises from the presentation of this subject is: Can the direction of the visual axes be so modified in the individual case as to change the pose of the head and body so as to relieve the person from the results of his physical peculiarity? To this an emphatic affirmative answer can be given. The eyes can be adjusted for any desired plane by a safe and speedy procedure. It may be said that, in the hands of one specially skilled in this procedure, the inconvenience and risk are scarcely as great as those resulting from vaccination as commonly practised.
Thus, by practical and judicious methods, the unfortunate positions of the eyes due to the hereditary form of the orbits may be rectified, and the handicap with which large classes of persons enter upon the course of life may be removed, thereby offering them that advantage and that staying quality in the contest for welfare and for success to which, by their native strength and inborn abilities, they are fairly entitled.
- An address delivered before the Section of Anthropology of The American Association for the Advancement of Science, at its session at Yale University, New Haven, December 27th, 1899.
- The Normal Plane of Vision in Relation to Certain Cranial Characteristics. 'Archives of Ophthalmology,' Vol. xxvi, No. 3, 1897.
- There is more in this statement than would at first appear, for the important question of the horopter must be included here, but this would add an element too extensive for present discussion.
- The subject of the horopter has already been referred to in the note to page 395. In regard to declinations, while it would be impossible to enter upon that complex subject here, it would be misleading were we to pass it by without the statement that the pose of the head is sometimes governed, even against the rule which it is sought here to point out, by the direction of the retinal meridians and hence in practice a knowledge of this subject would be essential to a full understanding of the subject under discussion.
- 'Transactions of the British Medical Association,' 1897.